Before, because you needed have one properties file per platform, you could set these in build.properties:

localSourceCheckoutDir=C:/workspace/org.eclipse.gef.tree
localSourceCheckoutDirExcludes=**/archive/**
# For windows, must be explicit about paths using correct
# slashes (/); dirs with spaces should be avoided
relengBuilderDir=C:/workspace/org.eclipse.gef.releng
relengBaseBuilderDir=C:/workspace/org.eclipse.releng.basebuilder
relengCommonBuilderDir=C:/workspace/org.eclipse.dash.common.releng
writableBuildRoot=C:/tmp/build

Now, set this in an optional build.local.xml file so it won't conflict with the server's "build from maps" version. This additional step is only needed if building from local sources; otherwise build.xml will work without modification on local or in Hudson!